Nickel(II) Complexes with Three-Dimensional Geometry 伪-Diimine Ligands: Synthesis and Catalytic Activity toward Copolymerization of Norbornene

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• 作者：Ping Huo ; Wanyun Liu ; Xiaohui He ; Hongming Wang ; Yiwang Chen
• 刊名：Organometallics
• 出版年：2013
• 出版时间：April 22, 2013
• 年：2013
• 卷：32
• 期：8
• 页码：2291-2299
• 全文大小：437K
• 年卷期：v.32,no.8(April 22, 2013)
• ISSN：1520-6041

文摘

A series of three-dimensional geometry 9,10-dihydro-9,10-ethanoanthracene-11,12-diimines (L1鈥揕4) and their nickel(II) dibromide complexes (C1鈥揅4) were synthesized and characterized. The nickel complexes C1鈥揅4, with three-dimensional geometry, exhibited very high activities for norbornene (NB) homopolymerization with only B(C₆F₅)₃ as cocatalyst,: for C2 even up to 5.53 脳 10⁷ g of polymer/((mol of Ni) h). To investigate the activation of polar monomer, complexes C2 and C3 were selected for copolymerization of NB and 5-norbornene-2-yl acetate (NB-OCOMe) in relatively high activities (1.6鈥?.8 脳 10⁵g of polymer/((mol of Ni) h)) and high molecular weights ((0.2鈥?.8) 脳 10⁵ g/mol) as well as narrow molecular weight distributions (MWD < 2 for all polymers) depending on the variation of feed ratios. The reactivity ratios of the NB and NB-OCOMe monomers for C2/B(C₆F₅)₃ system by the Kelen鈥揟眉d枚s method were determined to be r_NB-OCOMe = 0.05 and r_NB = 6.72, respectively. Moreover, the mechanism of polymerization catalyzed by the novel three-dimensional geometry nickel(II) complexes was presented and supported by an end group analysis of the polymer and density functional theory (DFT) calculations of the reaction. The substituent effect of the catalysts and the interaction between Ni²⁺ and NB were discussed, and the results showed that 伪-diimine nickel complexes with greater steric hindrance and smaller HOMO鈥揕UMO gaps could achieve higher reactivity.